1. Field of the Invention
The present invention relates to the field of wave transmission lines. More particularly, the invention relates to branched stripline circuits with impedance matching.
2. Description of the Prior Art
Stripline power dividers having a broadside input port with a pair of overlapping stripes spaced by a dielectric layer and diverging in opposite directions transversely of the input stripes to a pair of output ports individual to the stripes are well known, as is the connection of the stripes in the region of their divergence by lossy material to suppress odd mode electric fields between the stripes. It is also well known to taper the stripes and configure the lossy material in this region with a variety of shapes and provide desired impedance matching for the ports while suppressing odd mode fields.
In one prior art stripline power divider of this nature, the dielectric layer between the stripes has a plurality of bores extending between the stripes where they overlap just before divergence, the bores being filled with the lossy material. This construction has particularly effective transmission and impedance matching characteristics, particularly in comparison with a similar divider having a rectangular block of lossy material inserted in the dielectric layer where the stripes overlap and where they diverge. However, this construction with bores is somewhat expensive to construct since the bores are very small and difficult to fill with lossy material. This difficulty is avoided by a power divider configuration having diverging stripes, which are on the same side of the dielectric layer and diverge from an input stripe on this side, by providing a generally triangular opening or slot through the dielectric layer where the stripes initially diverge, this opening being filled with a piece of lossy material conforming to the opening. However, it is difficult in this configuration to give the lossy material the exact size and shape of the opening, particularly where the stripes and slot have a nonlinear taper. As a result, the material either does not effectively contact the stripes, resulting in improper odd mode suppression, or overlaps the stripes, resulting in undesired even mode suppression.